Electronic Assembly with Three Dimensional Inkjet Printed Traces

ABSTRACT

One method of making an electronic assembly includes mounting one electrical substrate on another electrical substrate with a face surface on the one substrate oriented transversely of a face surface of the other substrate. The method also includes inkjet printing on the face surfaces a conductive trace that connects an electrical contact on the one substrate with an electrical connector on the other substrate. An electronic assembly may include a first substrate having a generally flat surface with a first plurality of electrical contacts thereon; a second substrate having a generally flat surface with a second plurality of electrical contacts thereon, the surface of the second substrate extending transversely of the surface of said first substrate; and at least one continuous conductive ink trace electrically connecting at least one of the first plurality of electrical contacts with at least one of the second plurality of electrical contacts.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of and claims priority to U.S. patentapplication Ser. No. 13/591,719, filed Aug. 22, 2012. Said applicationherein incorporated by reference.

BACKGROUND

Integrated circuits (“IC's”) are ubiquitous in modern electricalproducts. Currently most integrated circuits are formed in individualsemiconductor units called dies or dice. Each semiconductor dietypically includes a silicon substrate block having multiple internaland/or external circuit layers. The circuit layers are usually formed byphotolithographic or screen printing processes. The various circuits inthese circuit layers may be electrically connected to a metal leadframe. The die and lead frame are often encased in a protective materialsuch as epoxy. One or more electrical contacts provided by the leadframe are formed on or project from the surface of the die. Theelectrical contacts allow the circuitry in the die to be electricallyconnected to other electronics.

Modern electronic assemblies usually include a number of integratedcircuits dies and other electronic devices that are electricallyconnected by a printed circuit board (PCB) or other interconnectapparatus such as ceramic multilayer interconnect boards (“MIB's”). ICdies are typically box shaped and have two oppositely positioned largestfaces. The dies are usually mounted on a PCB with one of the largestfaces of the die abutting a face surface of the PCB.

A process known as wire bonding is most often used to connect IC dies toa printed circuit board. With wire bond connection, connection points orbumps located on the top face of a die are soldered to thin bond wires.The other ends of the bond wires are soldered to contact pads on thePCB.

In another widely used process, solder balls are formed on contact areason one of the large face surfaces of a die. These solder balls are thenplaced in contact with corresponding contact pads on a PCB. The die andPCB are then heated. Heating causes the solder balls to bond with thecontact pads on the PCB thus physically and electrically connecting thedie to the PCB.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of an electronic assembly having anelectronic device mounted on an electrical substrate.

FIG. 2 is a side elevation view of the electronic assembly of FIG. 1.

FIG. 3 is a top plan view of the electronic assembly of FIG. 1.

FIG. 4 is an isometric view of first and second stacked electronicdevices connected to an electrical substrate.

FIG. 5 is a flow diagram illustrating a method of making an electronicassembly.

DETAILED DESCRIPTION

FIGS. 1-3, in general, disclose an electronic assembly 10 that includesa substrate 20 with at least one die 50 connected to the substrate 20 byan attachment layer 76. The substrate 20 has a first face surface 22with electrical contacts 24, 26, 28, etc., positioned on it. The die 50has a first face surface 52 and a second face surface 54 extendinggenerally perpendicular to the first face surface 52. Electricalcontacts 60, 62, 64, 66, etc. are positioned on the die first facesurface 52. The attachment layer 76 is positioned between and physicallyconnects the substrate first face surface 22 and the die second facesurface 54. The attachment layer has a first face surface 77 positionedsubstantially perpendicular to the substrate first face surface 22 andsubstantially parallel to the die first face surface 52. A conductivetrace, e.g. 80 extends between electrical contacts, e.g. 24, 60 on thefirst faces 22, 52 of the substrate 20 and die 50. The trace 80 isformed from electrically conductive ink dispensed from an inkjetprinthead 12.

A method of making an electronic assembly 10 is also disclosed. Thismethod, in general, includes mounting one electrical substrate 50 onanother electrical substrate 20 with a face surface 52 on the onesubstrate 50 oriented transversely of a face surface 22 of the othersubstrate. The method also includes inkjet printing on the face surfaces52, 22 a conductive trace 80 that connects an electrical contact 60 onthe one substrate 50 with an electrical contact 24 on the othersubstrate 20.

Having thus generally described an electronic assembly and a method ofmaking it, certain embodiments of an electronic assembly and method ofmaking it will now be described in detail

FIGS. 1-3 illustrate an electrical assembly 10 which includes asubstrate 20 having a generally flat first face surface 22. A pluralityof electrical contacts (sometimes referred to herein as connectors) 24,26, 28, 30, 32, 34, 36 (only 24 and 26 are shown in FIG. 3) are providedon the first face surface 22. A second substrate is mounted on the firstsubstrate. In the embodiment shown in FIGS. 1-3, the second substratemay be an electronic device such as a first die. The first die 50 has agenerally flat first face 52, which may be one of the two largest facesof the die 50. The first die 50 has a second face surface 54 extendinggenerally perpendicular to the first face surface 52. The second facesurface 54 is sometimes referred to herein as the “bottom face surface.”First die 50 has a generally flat third face surface 56 positionedgenerally perpendicular to the first face surface 52 and parallel to thesecond face surface 54. Third face surface 56 is sometimes referred toherein as the “top face surface.” The die first face surface 52 may havea sensor 58 operably mounted thereon. The sensor 58 may be, for example,a conventional sound, thermal, motion or light sensor. Also provided onthe first face surface 52 are a plurality of electrical contacts 60, 62,64, 66, 68, 70, 72. The bottom face surface 54 of the first die 50 isattached to the first face surface 22 of the substrate 20 by a layer ofattachment materials 76 which may comprise conventional die attachmentmaterial such as epoxy or solder or other attachment material now knownor later developed.

The electrical contacts on the substrate 20 are connected to theelectrical contacts on the first die 50 by a plurality of electricaltraces 82, 84, 86, 88. Some of the electrical traces, e.g. 34, 36, onthe substrate 22 may be connected directly to one another as by aconductive trace 90. Similarly, conductors 70, 72 on die 50 may beconnected to one another by a trace 92.

The above-described conductive traces may all be inkjet printed traces.The printing of conductive traces on a two dimensional surface using aninkjet printer is known in the art as described in U.S. patentapplication publication no. U.S. 2010/0059251 published Mar. 11, 2010for “Printed Circuit Board and Manufacturing Method” of Sergey Remizov,et al.; U.S. 2010/0149249 published Jun. 17, 2010 for “Surface TreatmentMethod, Circuit Lines Formation Method, Circuit Lines FormationApparatus and Printed Circuit Board Formed Thereby” of Yoon-Ah Baik, etal.; U.S. 2011/0042125 published Feb. 24, 2011 for “Conductive Ink,Method of Preparing Medal Wiring Using Conductive Ink, and PrintedCircuit Board Prepared Using Method” of Jong-Hee Lee, each of which ishereby incorporated by reference for all that is disclosed therein.However, to applicants' knowledge, three dimensional inkjet printing ofconductive traces on an electrical assembly 10 was first developed byapplicant.

Various ink formulations that may be used to inkjet print conductivetraces are known in the art, such as those disclosed in the above patentpublications incorporated by reference. Another such ink formulationsuitable for printing conductive traces is disclosed in U.S. PatentApplication U.S. 2010/0178420 published Jul. 15, 2010, which is herebyincorporated by reference for all that is disclosed therein. Othersuitable inkjet ink formulations are commercially available from variousmanufacturers such as DuPont, Microcircuit Materials, 14 T. W. AlexanderDr., Research Triangle Park, N.C. 27709. One such DuPont inkjet ink issold under the product designation 5000 Silver Conductor.

As illustrated by FIG. 1, inkjet traces 80, 82, 84, 86, 88 connect,respectively, contacts 24 and 60, 26 and 62, 28 and 64, 30 and 66, and32 and 68. Each of these traces 80, 82, 84, 86, 88 includes a firstportion, e.g. 81, contacting the first face surface 52 of the die 50 anda second portion, e.g. 83, contacting the first face surface 22 of thesubstrate 20. A third portion, e.g., 85, of each trace connects thefirst and second portions 81, 83 and contacts the surface 77 of theattachment material 76. (However, in some embodiments the substrate 20is mechanically connected to the die 50 without use of attachmentmaterial 76, as by joints or friction fit or nail or screw likestructures. In such cases there may be no third trace portion 85.) Inmany cases, the surface 77 of the attachment material 76 issubstantially coplanar with the first die first face surface 52. Some ofthe conductive traces, e.g. 92, extend between two contact points 70, 72on the die 50. Other traces, e.g. 90, extend between two contact points34, 36 on the first substrate surface 22. In some embodiments, each ofthe conductive traces is continuously printed by an inkjet sprayhead. Inother words, there are no time gaps between printing of the variousportions of the trace. Each trace, e.g. 80, as thus continuouslyprinted, is physically continuous from the contact, e.g. 24, on thefirst face surface 22 of the substrate 20 to the contact, e.g. 60, onthe first face surface 52 of die 50.

One printhead assembly is shown at 11 in FIG. 1. The printhead assemblymay include a printhead 12 having at least one nozzle 13, FIGS. 2 and 3,operably connected to a reservoir. The reservoir may be provided withinthe printhead 12 itself or may be located remotely and connected as byfluid conduit to the printhead 12. Inkjet printheads are well known inthe art and any such printhead capable of forming a trace of suitabledimensions may be used for this purpose. The printhead 12 may be mountedon a displaceable support assembly 14 which, in one embodiment, enablesthe printhead to be displaced laterally, parallel to the XX axis,longitudinally, parallel to the YY axis, or vertically, parallel to theZZ axis. The printhead 12 may also be rotatable about one or more axes,such as, for example, axis AA that is parallel to the lateral axis XX.The printhead 12 may thus be moved vertically, laterally andlongitudinally to produce rectilinear conductive traces extendingbetween substrate face surface 22 and die face surface 52. In otherembodiments the printhead may be displaced about multiple axes at thesame time to produce curved traces. In making the transition fromvertical printing of the die face surface 52 to the substrate facesurface 22, the printhead 12 may first be positioned such that the sprayjet 15 is directed perpendicular to surfaces 52 and 77, then rotatedabout axis AA as best shown in FIG. 2, to produce a portion of the tracenear the intersection line 16 of the attachment material face surface 77(or the die first face surface 52 in embodiments where there is noattachment material) and the substrate first face surface 22. Next, theprinthead 12 may be rotated to a position such that the spray 15 is onlyperpendicular to the first face surface 22 of the substrate 20 while itis being displaced in either the lateral (XX) or longitudinal (YY)direction. In this embodiment the printhead 12 rotates about 90° duringthe transitional printing period. In another embodiment (not shown), theprinthead 12 is mounted at a fixed angle with respect to the surfaces 22and 52 such that the inkjet spray 15 contacts each of these surfaces atan angle of about 45°. In this embodiment, rotation of head 12 aboutaxis AA is not required.

Robotics and machine vision systems for producing the above described orother displacements of a printhead 12, e.g., pick and place machinerobotics, are well known in the industry and will thus not be furtherdescribed herein.

FIG. 4 illustrates an electronic assembly 110 similar to electronicassembly 10 described above except that a second electronic device suchas a second die 160 is mounted on top the first electronic device (firstdie 150). In this assembly, the second die 160 has a vertically andlaterally extending first face surface 162, a laterally andlongitudinally extending second face surface 164 and a laterally andlongitudinally extending top face surface 166. In this embodiment, thethird (top) face surface 156 of the first die 150 is attached to thesecond (bottom) face surface 164 of the second die 160 by a secondadhesive layer 142 having a face surface 143.

The first face surface 122 of substrate 120 may have contacts 170, 172,174 provided thereon. The first face surface 152 of first die 150 mayhave contacts 180, 182, 184 provided thereon. The first face surface 162of second die 160 may have contacts 190, 192, 194, 196, 198 providedthereon. A sensor 200 or other electrical component may be provided onthe upper die 160. A trace 202 may extend from the second die contact190 to the substrate contact 170. In this case the trace is adhered tosurfaces 162, 143, 152, 77 and 22. Another trace 204 may connectcontacts 172, 182 and 194 located on the first surfaces of substrate120, first die 150, and second die 160, respectively. Conductive trace206 connects contact 174 on substrate surface 122 with contact 184 onfirst die first surface 152. A trace 208 connects two electricalcontacts 196, 198 located on the second die first surface 162. A trace210 connects contact 180 on first die surface 152 to contact 192 onsecond die first face surface 162. The same printhead assembly describedabove with reference to FIGS. 1-3, or another printhead assembly capableof displacement in three dimensions may be used to provide the inkjetprinted traces illustrated in FIG. 4.

It is to be understood that terms such as vertical, lateral, up, down,bottom, top and the like that are sometimes used in an absolute sense toindicate an orientation in a gravitational field are not used in thatsense herein. Rather such terms are used in a relative sense, usuallywith reference to the drawings, to indicate the relationship betweenvarious components or parts thereof.

The drawings show electronic assemblies 10 and 110 that include a singledie mounted on a PCB and a pair of vertically stacked dies mounted on aPCB. Other embodiments in which multiple dies or other devices aremounted on a PCB or other interconnect boards in various orientationsand stacking arrangements have not been specifically described to avoidunnecessary repetition. However it will be understood that the novelconcepts disclosed herein also apply to such alternative configurations.

As used herein the term “electrical substrate” refers to an objecthaving at least one generally flat face that has an electrical contactthereon. Thus an “electrical substrate” may be an electrical connecterboard such as a wiring board, printed circuit board, ceramic or otherMIB, or other interconnect structure. The term “electrical substratealso encompasses semiconductor dies and various other electronic devicessuch as wafers, semiconductor packages, ceramic or other multilayerinterconnect boards (”MIB's), flex tape, passive resistors, passivecapacitors, passive inductors, electrical housings and connectors. Inthe specifically described embodiments of FIGS. 2-4 the second substrateis referred to as a die 50, but it is to be understood that manydifferent types of electrical substrates, such as those listed above,could be substituted for die 50. Similarly, various other electronicsubstrates could be substituted for dies 150, 160.

The first and second substrates 20, 50 shown in FIGS. 1-3 are describedas having generally perpendicular face surfaces 22, 52. In someembodiments surfaces 22 and 52 may not be truly perpendicular. Forexample one may be oriented at an angle of 75°, etc., relative to theother. The term “transversely” as used herein refers to surfacespositioned perpendicular to one another and to other orientations ofplanar, nonparallel surfaces.

Most inkjet printable inks require heat for proper curing after beingprinted. Accordingly once an electronic assembly 10, 110 has beenprinted it may be transferred to a curing environment such as a boxoven, IR belt furnace, or the like (not shown) for curing at anappropriate temperature for an appropriate curing period that willdepend upon the ink that is used.

One method of making an electronic assembly is illustrated in the flowchart of FIG. 5. The method may include mounting one electricalsubstrate on another electrical substrate with a face surface on the onesubstrate oriented transversely of a face surface of the othersubstrate, as shown at 201. The method may further include inkjetprinting on the face surfaces a conductive trace that connects anelectrical connector on the one substrate with an electrical connectoron the other substrate, as shown at 202.

Although certain embodiments of an electronic assembly having inkjetprinted traces and a method of making an electronic assembly have beendescribed in detail herein, it is to be understood that the electronicassembly and method are not limited to these specific embodiments andmay be otherwise constructed. Many alternative embodiments of thedisclosed assembly and method will be apparent to those skilled in theart after reading this disclosure. It is intended that the appendedclaims be broadly construed so as to encompass such alternativeembodiments, except to the extent limited by the prior art.

What is claimed is: 1-15. (canceled)
 16. A method of making anelectronic assembly comprising: mounting one electrical substrate onanother electrical substrate with a face surface on the one substrateoriented transversely of a face surface of the other substrate; andinkjet printing on the face surfaces a conductive trace that connects anelectrical contact on the one substrate face surface with an electricalcontact on the other substrate face surface.
 17. The method of claim 16wherein said inkjet printing a conductive trace comprises: moving aprint head parallel to the face surface on the one electrical substratein at least one of a vertical direction and a lateral direction; andmoving the print head parallel to the face surface on the otherelectrical substrate in at least one of the lateral direction and alongitudinal direction.
 18. The method of claim 16 wherein said inkjetprinting a conductive trace further comprises rotating the print headabout an axis.